Abstract

MORALES, Cecilio et al. Average shear wave velocities in the first 30 m depth (vs30 vs30), inferred from the topographic splope in the metropolitan area of Caracas. Rev. Fac. Ing. UCV [online]. 2011, vol.26, n.2, pp.161-168. ISSN 0798-4065.

Average shear wave velocity in the upper 30 m (Vs30) is one of the geophysical parameters used at great length for estimating the site seismic responses, and it was employed as an index in the parametric 1D site response study for the Caracas Seismic Microzoning Project. It is known that shear wave velocity is related with stiffness (shear modulus) and density and it becomes apparent in endurance to erosion and in topographic slope (high topographic slope: high Vs30 value), leading to recent published relations between Vs30 and relief. This methodology was taken for the Caracas Seismic Microzoning Project, in order to extend the Vs30 distribution map to the out-valley zones with little geotechnical information, by means of GIS technologies. In the new map we can infer differential rock weathering at hills. These results were added to those obtained with a NSPT-Vs relationship for the Caracas sedimentary valley, leading to a Vs30 integrated map for the Caracas Metropolitan Area (AMC). Then, we could have to our disposal a necessary input, together with other technical data and the parametric study, for defining microzones in the whole AMC.

Keywords : Vs30; Topographic slope; Seismic microzoning; Average shear wave; Caracas.